Manufacturing method of light emitting device and manufacturing device thereof

ABSTRACT

It is an object of the present invention to provide a light emitting device having a structure wherein oxygen and moisture are prevented from reaching to the light emitting device, and to provide a manufacturing method thereof. It is another object of the present invention to seal a light emitting device in fewer steps without encapsulating a desiccant. 
     The present invention provides a structure in which a pixel region  13  is surrounded by a first sealing material (having higher viscosity than a second sealing material)  16  including a spacer (filler, minute particles and/or the like) which maintains a gap between the two substrates, filled with a few drops of the transparent second sealing material  17   a  which is spread in the region; and sealed by using the first sealing material  16  and the second sealing material  17.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a manufacturing device provided with apasting structure for a sealing substrate which seals elements(typically, a semiconductor element, a light emitting element, a memoryelement, a sensor, or a photoelectric transducer, each formed from athin film transistor (hereinafter referred to as a TFT)). Moreparticularly, the present invention relates to a pasting device for asealing substrate which seals a light emitting element on the occasionof manufacturing a light emitting device which has a layer containing anorganic compound as a light emitting layer.

2. Description of the Related Art

Recently, researches on a light emitting device comprising an EL elementas a self luminous light emitting element are revitalized. This kind oflight emitting device is called an organic EL display or an organiclight emitting diode. Such light emitting devices have characteristicssuch as high response speed which suitable for displaying moving images,low voltage drive, and low power consumption, so that the light emittingdevices draw keen attention as new-generation displays for mobilephones, personal digital assistants (PDA), and the like.

An EL element includes a layer containing an organic compound whereinelectro luminescence can be obtained by applying electric field thereto,an anode, and a cathode. The luminescence with an organic compound canbe broadly classified into two types: one is emitted when the singletexcited state returns back to the ground state (fluorescent light) andanother that is emitted when the triplet excited state returns back tothe ground state (phosphorescent light). Either or both types of theluminescence can be used for a light emitting device manufactured by afilm forming mechanism and a film formation method according to thepresent invention.

A light emitting device has no problem with the viewing angle because itis a self luminous type, different from a liquid crystal display device.Accordingly, a light emitting device is better suited for outdoor usethan a liquid crystal device, and various usages are suggested.

An EL element has a structure wherein an EL layer is sandwiched betweena pair of electrodes, and an EL layer generally has a laminatedstructure. A laminated structure of “a hole transporting layer/a lightemitting layer/an electron transporting layer” can be given as a typicalstructure. This structure brings extremely high luminous efficiency, sothat most of the light emitting devices developed nowadays employs thisstructure.

Further, structures having the following layers laminated in order overan anode are also applicable: a hole injecting layer/a hole transportinglayer/a light emitting layer/an electron transporting layer, and a holeinjecting layer/a hole transporting layer/a light emitting layer/anelectron transporting layer/an electron injecting layer. Fluorescentpigments or the like may also be doped into the light emitting layer.Furthermore, these layers may be formed from either of low molecularweight materials or polymer materials.

Note that, in this specification, all the layers provided between acathode and an anode are referred to as EL layers generically.Accordingly, the above layers: a hole injecting layer, a holetransporting layer, a light emitting layer, an electron transportinglayer, and an electron injecting layers shall be all included in an ELlayer.

Furthermore, in this specification, a light emitting element formed froma cathode, an EL layer, or an anode is referred to as an EL element. TheEL element is formed by two systems: a system in which an EL layer isformed between two types of stripe electrodes arranged so as to cross atright angles to one another (simple matrix system); and another systemin which an EL layer is formed between a pixel electrode and a counterelectrode, which are arranged in matrix and connected to a TFT (activematrix system). However, when the pixel density is increased, an activematrix system wherein a switch is provided for each pixel (or a dot) isconsidered advantageous because it is available for low voltage drive.

Further, an EL material forming an EL layer deteriorates extremelyeasily, and is easily oxidized or absorbs moisture. Therefore, a lightemitting element has a problem of a decline in luminance or shortlifetime.

Accordingly, in prior art, a light emitting element is covered with anencapsulating can; the interior is filled with dry air; and a desiccantis further adhered thereto, thereby preventing oxygen or moisture fromreaching to the light emitting element.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a light emittingdevice having a structure wherein oxygen and moisture are prevented fromreaching to the light emitting device, and to provide a manufacturingmethod thereof. It is another object of the present invention to seal alight emitting device in fewer steps without encapsulating a desiccant.

The present invention further provides a pasting device which can matesubstrates having unevenness or flexible substrates to a substrateprovided with a light emitting element.

A substrate provided with a light emitting element and a transparentsealing substrate are pasted together in the present invention. When twosubstrates are pasted together, the entire surface of a pixel region iscovered with a second sealing material that is transparent, surroundedby a first sealing material including a spacer (filler, minute particlesand/or the like) which maintains a gap between the two substrates, andsealed with a first sealing material (having higher viscosity than thesecond sealing material) and the second sealing material.

When the first sealing material is patterned to have a shape of square,or U-shape, and the second sealing material with a lower viscosity isapplied to paste the two substrates, air bubbles may be remain at thecorners.

Especially, film-like substrates which are soft like plastic havetendency for air bubbles to generate easily.

In the case where two film substrate are pasted together by applying adrop of the second sealing material to the central part of thesubstrate, the sealing material spreads concentrically, so that it isdifficult to make the sealing material spread all over.

Accordingly, in the present invention, the pattern of the first sealingmaterial shall be a pattern without bending (bar shape) but not square,or U-shape. The corners are provided with opening portions (on fourparts); a rather larger amount of a drop of the second sealing materialis applied to the central part surrounded by the first sealing material,and a rather smaller amount of a few drops thereof are applied to thesurrounding area.

When two substrates are pasted together, the second sealing materialwith a low viscosity is squeezed out to the direction of the openingportions which are provided at the corners, thereby sealing without airbubbles mixed in the pixel region. It is preferable that the surface ofthe substrate, which is to be sealed, shall preferably be well flattenedand smooth thereby preventing air bubbles from mixing in.

Especially, that helps in pasting thin substrates like film substrates.Further, that helps in pasting a thin separated layer (without asubstrate) which is separated from a glass substrate, to a filmsubstrate. In an experiment where more than a drop of the second sealingmaterial is applied, the second sealing material does not spread allover due to the lack of the amount applied to the central part; or thesecond sealing material applied to the periphery spreads exceedinglyand/or reaches to the edge (or the back) of the substrate.

In view of the above problem, the present invention provides amanufacturing device in which a surface of a substrate tray or asubstrate stage is coated with Teflon or diamond like carbon(hereinafter referred to as DLC) thereby making the substrate hardlyadhere to the substrate. That lessens the problem that the sealingmaterial spreads excessively and reaches to the edge (or the back) ofthe substrate. Alternatively, the substrate tray or substrate stageitself may be formed from a material which hardly adheres to the secondsealing material. A manufacturing device according to the presentinvention provides broad range of pasting conditions on such as theamount of the second sealing material to be applied, the position wherethe sealing material is applied, the bonding pressure, or the like.

The first sealing material with higher viscosity maintains a gap betweensubstrates with a spacer, and shapes the second sealing material to haveflatness. The first sealing material can be a mark for dividing thesubstrates. For example, in the case where plural panels aremanufactured from one substrate, the substrate can be divided along thefirst sealing material.

When a substrate is hit by external shocks, the portion of the firstsealing material disposed outside the pixel area shall be affected most,so that the pixel area itself can be unaffected. Thus, a light emittingdevice can have more mechanical strength by using the structureaccording to the present invention.

A light emitting element can be protected from oxygen and moisture owingto be sealed with the first sealing material, the second sealingmaterial, and the substrates. Note that, a pair of substrates ispreferably pasted together under reduced pressure or in a nitrogenatmosphere.

A constitution of the present invention in this specification disclosesa manufacturing method of a light emitting device including a pixelportion provided with a plurality of light emitting elements having afirst electrode, an organic compound layer in contact with a top portionof the first electrode, and a second electrode in contact with a topportion of the organic compound layer, between a pair of substrates, atleast one of which is transparent, the manufacturing method of a lightemitting device comprising the steps of:

-   -   forming a pixel portion on one of the substrates;    -   figuring a first sealing material having a bar shape on the        other substrate;    -   applying a plurality of drops of a second sealing material        having lower viscosity than the first sealing material to a        region surrounded by the first sealing material so that an        amount of drops differs depending on a region to be applied to;        and    -   arranging the first sealing material to surround the pixel        region, and filling a space between at least a pair of the first        sealing materials with the second sealing material for pasting a        pair of substrates.

In the above constitution, the second sealing material is applied atleast to a central part of a pixel portion and to the positionsurrounding the central part with a constant distance therefrom; and anamount of the second sealing material applied to the central part ismore than an amount applied to the position surrounding the centralpart.

In each of the above constitutions, the first sealing material hasopening portions at least at four corners.

In each of the above constitution, the first sealing material includes aspacer for maintaining a gap between a pair of substrates.

In each of the above constitutions, the second sealing material isexposed at the opening portions, and edges of the exposed second sealingmaterial are curved.

In each of the above constitutions, the second sealing material isexposed at the opening portions, and edges of the exposed second sealingmaterial are protrudes from the opening portions.

Another constitution of the manufacturing device in this inventiondiscloses a manufacturing method of a light emitting device including apixel portion provided with a plurality of light emitting elementshaving a first electrode, an organic compound layer in contact with atop portion of the first electrode, and a second electrode in contactwith a top portion of the organic compound layer, between a pair ofsubstrates, both or either of which is transparent, the manufacturingmethod of a light emitting device comprising the steps of:

-   -   forming a pixel portion on one of the substrates;    -   figuring a first sealing material having a bar shape on the        other substrate;    -   applying a plurality of drops of a second sealing material        having lower viscosity than the first sealing material to a        region surrounded by the first sealing material so that an        amount of drops differs depending on a region to be applied to;    -   filling a space between the first sealing materials facing one        another, by spreading the second sealing material under pressure        in the case where a pair of substrates is pasted together as the        pixel region is surrounded by the first sealing material.    -   curing the first sealing material and the second sealing        material.

In the above constitution, the process of curing the first sealingmaterial and the second sealing material is performed by exposure toultraviolet radiation or by heat.

In the above constitution, a pair of substrates is divided verticallyafter curing the first sealing material and the second sealing material.

A pasting device according to the above manufacturing method is also oneof the present invention, and a manufacturing device including a pastingdevice which mates a pair of substrates together with a predetermineddistance therebetween, comprising:

-   -   two substrate holders facing one another;    -   means for squashing a sealing material by applying pressure to        put the two substrate holders together.    -   a substrate holders covered with a film containing        fluoroplastics.

In the above constitution, the film comprising fluoroplastics is formedof one selected from the group consisting of: polytetrafluoroethylene,tetrafluoroethylene-hexafluoropropylene copolymer,polychlorotrifluoroethylene, tetrafluoroethylene-ethylene copolymer,polyvinyl fluoride, and polyvinylidene fluoride.

Another constitution of the manufacturing device in this inventiondiscloses a manufacturing device including a pasting device which matesa pair of substrates together with a predetermined distancetherebetween, comprising:

-   -   two substrate holders facing one another;    -   means for squashing a sealing material by applying pressure to        put the two substrate holders together.    -   a two-sided tape for securing substrates to the two substrate        holders

Further, in the above construction, the pasting device shall be providedwith a light source, and in which both or either of the two substrateholders are formed of a material transparent to light. A pair ofsubstrates is pasted together, followed by exposing a sealing materialto light from the light source through one substrate holder for curingthe sealing material. In addition, in the case of fixing a substrateusing the two-sided tape in which adhesion is weakened by exposure tolight, the sealing material can be cured by exposure to light and thetwo-sided tape can be peeled from the substrate holders concurrently.

Moreover, in the above constitution, the pasting device shall beprovided with light source, and in which both or either of the twosubstrate holders are formed of a material transparent to light. Furtherone of the surface of the substrate holders facing a transparent oneshall be a mirrored surface which reflects light. Thus, light which passthrough the one of the substrate holders can pass through the pair ofthe substrates and can be reflected and applied to the sealing materialonce again.

Furthermore, in the above construction, either or both of the twosubstrate holders shall be provided with a heating means. A sealingmaterial is cured by heating after a pair of substrates is pastedtogether. In addition, in the case of fixing a substrate using thetwo-sided tape in which adhesion is weakened by heating, the sealingmaterial can be cured by heating and the two-sided tape can be peeledfrom the substrate holders concurrently.

An EL element includes a layer containing an organic compound whereinelectro luminescence can be obtained by applying electric field thereto,an anode, and a cathode. The luminescence with an organic compound canbe broadly classified into two types: one is emitted when the singletexcited state returns back to the ground state (fluorescent light) andanother that is emitted when the triplet excited state returns back tothe ground state (phosphorescent light). Either or both types of theluminescence can be used for a light emitting device according to thepresent invention.

A light emitting element (EL element) having an EL layer has a structurewherein an EL layer is sandwiched between a pair of electrodes, and anEL layer generally has a laminated structure. A laminated structure of“a hole transporting layer/a light emitting layer/an electrontransporting layer” can be given as a typical structure. This structurebrings extremely high luminous efficiency, so that most of the lightemitting devices developed nowadays employs this structure.

Another structure in which “an anode, a hole transporting layer, a lightemitting layer, and an electron transporting layer” or “an anode, a holeinjecting layer, a hole transporting layer, a light emitting layer, anelectron transporting layer, and an electron injecting layer” arelaminated sequentially is also applicable. Fluorescent pigments may bedoped to the light emitting layer. For forming these layers, either alow molecular material or a high molecular material can be used. In thisspecification, an EL layer shall be a generic term used to refer to alllayers formed between a cathode and an anode. Therefore, each of theabove-mentioned hole injecting layer, hole transporting layer, lightemitting layer, electron transporting layer, and electron injectinglayer shall be an EL layer.

Further, as for a light emitting device according to the presentinvention, a driving method for a screen display is not particularlylimited and, for example, any one of a point sequential drive method, aline sequential drive method and a face sequential drive method may beused. Typically, the line sequential drive method shall be adopted and atime division gradation drive method or an area gradation drive methodmay appropriately be applied. A video signal to be inputted to a sourceline of the light emitting device may either be an analog signal or adigital signal. A driver circuit or the like may appropriately bedesigned in accordance with the video signal. The present invention canbe applied not only to an active matrix light emitting device, but alsoto a passive matrix light emitting device or other types of lightemitting devices.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A and 1B show a top view of a substrate before and after pasting(Embodiment Mode 1);

FIGS. 2A to 2C show a cross section of a manufacturing device(Embodiment Mode 1);

FIGS. 3A to 3D show a top view of a substrate before and after pasting(Embodiment Mode 2);

FIGS. 4A and 4B show a cross section of a manufacturing device(Embodiment Mode 2);

FIGS. 5A to 5J show a manufacturing process (Embodiment 1);

FIGS. 6A and 6B show a cross-sectional TEM picture of the substratebefore the separation (Embodiment 1);

FIGS. 7A and 7B show a cross-sectional TEM picture of the substrateafter the separation (Embodiment 1);

FIG. 8 shows a picture of a displaying panel (Embodiment 1);

FIGS. 9A and 9B show a structure of an active matrix EL display device(Embodiment 1);

FIGS. 10A and 10B show a structure of an active matrix EL display device(Embodiment 2);

FIGS. 11A and 11B show a top view of a substrate before and afterpasting (Embodiment Mode 2);

FIGS. 12A to 12H show examples of electronic devices (Embodiment 4)

FIGS. 13A and 13B show a top view of a substrate before and afterpasting (Embodiment Mode 1);

FIGS. 14A and 14B show a top view of a substrate before and afterpasting (Embodiment Mode 1); and

FIGS. 15A and 15B show a cross section of a manufacturing device(Embodiment Mode 2).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiment Mode 1

FIG. 1A shows a top view of an example of a sealing substrate (a secondsubstrate 12) before pasting. FIG. 1A further shows an example ofmanufacturing a light emitting device having a pixel area from onesubstrate.

Eight bars of a first sealing material 16 are formed first on the secondsubstrate 12 by using a dispenser; thereafter, a plurality of drops of asecond sealing material having a lower viscosity than that of the firstsealing material is applied thereon. Note that, a top view of the secondsubstrate with the second sealing material having dripped thereoncorresponds to FIG. 1A.

A first substrate, on which a pixel area 13 having light emittingelements, or a driver circuit portion 14, and a terminal area 15 areformed, is then pasted to the second substrate. A top view of a stateimmediately after pasting the pair of substrates is shown in FIG. 1B.Meanwhile, the viscosity of the first sealing material is high, so thatit squeezed out very little upon pasting. The viscosity of the secondsealing material is low, however, and the second sealing materialspreads out planarly upon pasting, as shown in FIG. 1B. The secondsealing material is squeezed out between the bars of the first sealingmaterial 16, that is, in the direction of an arrow in FIG. 1B, towardopenings. Air bubbles can thus be kept from existing in a region betweenthe bars of the first sealing material 16, which is filled with thesecond sealing material. The first sealing material 16 does not mix witha second sealing material 17 b, even if there is contact, and the firstsealing material 16 has a viscosity with which the position where it isformed is not changed by the second sealing material 17 b.

Further, the first sealing material 16 includes a spacer (filler, minuteparticles and/or the like) for maintaining a gap between the twosubstrates. Since the bars of the first sealing material 16 aresymmetrically disposed, loads are applied uniformly in a balancedmanner. Shocks from the outside can therefore be uniformly diffused.Each bar of the first sealing material has a symmetrical shape, and isdisposed symmetrically, and therefore a very constant gap between thesubstrates can be maintained. The first sealing material 16 is disposedin the plane of the substrate, in parallel with an x-direction or ay-direction.

When the two substrates are pasted together, a pattern shown in FIG.13A, in which the space between the bars of the first sealing material86 is be narrow may be applied so as not to cover a connection port inthe terminal area with a second sealing material 17 a being squeezedout. A top view of the state immediately after a pair of the substratesis shown in FIG. 13B. Alternatively, a pattern shown in FIG. 14A, inwhich bars of a first sealing material 96 are arranged oblique to thesides of the substrate may be applied so that a second sealing material17 a is not squeezed out and is prevented from running out of the sidesof the substrate. A top view of the state immediately after a pair ofthe substrates is pasted together is shown in FIGS. 14A and 14B. Notethat, since FIGS. 13A and 13B and FIGS. 14A and 14B have almost the samestructures as FIGS. 1A and 1B except for patterns of the bars of thefirst sealing material; like components are denoted by like numerals inFIGS. 1A and 1B.

It is preferable that the substrates be pasted together by a pastingdevice shown in FIGS. 2A to 2C as in a manner where the second sealingmember may cause no problem in spreading to the sides of the substrate.

FIGS. 2A to 2C show a cross section of a state before a pair ofsubstrates is pasted together; FIG. 2B shows a cross section of a stateimmediately after pasting the substrates; and FIG. 2C shows a crosssection of a state after pasting the substrates. In FIGS. 2A to 2C,reference numeral 21 denotes a first substrate holder; reference numeral22 denotes a second substrate holder; reference numeral 23 denotes afluoroplastic film; and reference numeral 24 denotes a lifting pin. Notethat, like components in FIGS. 2A to 2C are denoted by like numerals inFIGS. 1A and 1B.

The second substrate holder in the pasting device shown in FIGS. 2A to2C is coated with a fluoroplastic film typified by Teflon. By coatingthe second substrate holder with a fluoroplastic film which has littleadhesion with the second sealing material, the second substrate holdercan be prevented from firmly adhering with the second substrate evenwhen the second sealing material with a low viscosity reach to the sidesof the substrate or to the back of the substrate.

Note that, the second substrate holder 22 is provided with a concaveportion for clipping and fixing the second substrate 12. The secondsubstrate holder is further provided with the lifting pins 24 forremoving the substrate after pasting. The first substrate holder 21 isprovided with a fixing means (a fixing pin, a vacuum chuck, or the like)for fixing the first substrate. Moreover, the first substrate holder 21or the second substrate holder 22 may be provided with a heating meansfor curing the sealing material.

Embodiment Mode 2

An example of manufacturing a panel from one substrate is shown inEmbodiment Mode 1. Here, an example of manufacturing plural panels fromone substrate will be described with reference to FIGS. 3A to 3D.

Bars of a first sealing material 32 are formed first in a predeterminedlocation on a second substrate 31 by using a dispenser apparatus underan inert gas atmosphere. (See FIG. 3A.) A material that contains filler(diameter of 6 μm to 24 μm) and having a viscosity of 370 Pa·s is usedfor a translucent sealing material for the bars of the first sealingmaterial 32. Further, the first sealing material 32 can be formed byprint process because it has a simple sealing pattern.

Next, a transparent second sealing material 33 is dripped on the regionsurrounded by the bars of the first sealing material 32 (with openingsat least in four corners) (see FIG. 3B). A highly heat resistant UVepoxy resin (product name 2500 Clear, manufactured by Electro-LiteCorporation) having a refractive index of 1.50 and viscosity of 500 cpsis used here.

The first substrate, on which pixel areas 34 are formed, and the secondsubstrate provided with the bars of the sealing material are formed, arethen pasted together. (See FIG. 3C.) Note that it is preferable toperform annealing in vacuum immediately before pasting the pair ofsubstrates together by using the sealing material, thus performingdegasification. The second sealing material 33 is spread out so as tofill a space between the bars of the first sealing material 32. Due tothe shape and the arrangement of the bars of the first sealing material32, the second sealing material 33 can be made to fill the space withoutthe introduction of air bubbles. Thereafter, ultraviolet lightirradiation is performed to cure the first sealing material 32 and thesecond sealing material 33. Note that a heat treatment may also beperformed in addition to ultraviolet irradiation.

Note that, the first substrate 35 is a plastic substrate, and pluralkinds of TFTs are formed in matrix thereon, thereby forming a pixelregion. The second substrate 31 is also a plastic substrate.

Subsequently, the first substrate 35 is cut by using a cutting machinesuch as a rotating saw (See FIG. 3D). Here, four panels are formed fromone substrate.

An example of a pasting device different from the one in Embodiment Mode1 is shown in FIGS. 4A and 4B.

In FIGS. 4A and 4B, reference numeral 41 denotes a first substrateholder; reference numeral 42 denotes a second substrate holder;reference numeral 43 denotes a fluoroplastic film; reference numeral 44denotes a support; reference numeral 48 denotes a bottom plate; andreference numeral 49 denotes a light source. Note that, the likereference numerals in FIGS. 3A to 3D are used for the correspondingparts in FIGS. 4A and 4B.

The bottom plate 48 is formed of a material transparent to light so thatultraviolet radiation emitted from the light source 49 is transmittedthrough thereby curing the first sealing material 32 or the secondsealing material 33. A structure in which the sealing material isexposed to light transmitted through the bottom plate 48 and to theextra light reflected by the mirrored first substrate may be applied,thereby exposing the sealing material effectively. The second substrate31 which is to serves as a sealing substrate is cut into a desired sizebeforehand and arranged on the support 44. Note that, a glass substratecoated with a fluoroplastic film is used here for the support 44. Whenthe substrates are pasted together, after the first substrate holder andthe second substrate holder are lowered, and the first substrate and thesecond substrate are pasted together by applying pressure, therebycuring the sealing material with ultraviolet radiation directly appliedthereto without modification, as shown in FIGS. 4A and 4BB.

As with the pasting device shown in FIGS. 4A and 4B, since the secondsealing material is coated with the fluoroplastic film, it is not adhereto the support 44 although it spreads to the side of the secondsubstrate or to the back of the substrate.

An example of a pasting device different from the one in FIGS. 4A and 4Bis shown in FIGS. 15A and 15B.

In FIGS. 15A and 15B, reference numeral 41 denotes a first substrateholder; reference numeral 42 denotes a second substrate holder;reference numeral 44 denotes a support; reference numeral 48 denotes abottom plate; reference numeral 49 denotes a light source; and referencenumerals 60 and 61 denote two-sided tapes. Note that, the same referencenumerals in FIGS. 4A and 4B are used for the corresponding parts inFIGS. 15A and 15B. Further, the same reference numerals in FIGS. 3A to3D are used for the corresponding parts in FIGS. 15A and 15B.

In FIGS. 15A and 15B, the first substrate 35 is fixed to the substrateholder 41 with the two-sided tape 60. The second substrate is fixed tothe support 44 with the two-sided tape 61. The two-sided tapes 60 and 61with adhesion force which is deteriorated by ultraviolet radiation, orthe ones with adhesion force which is deteriorated by heat may be used.After the first substrate holder and the second substrate holder arelowered, the substrate 35 and the substrate 31 are pasted together withthe two-sided tapes 60 and 61 by applying pressure. The sealing materialis cured by being exposed to ultraviolet radiation without modification.When a tape with adhesion force which is deteriorated by ultravioletradiation is used, the adhesion force can be deteriorated; after thepasting process, the panels can be removed easily from the substrateholder, and further, the two-sided tapes can be peeled off from thepanels.

This embodiment mode can be combined freely with Embodiment Mode 1.

The present invention using the above described structure will bedescribed more precisely with embodiments below.

Embodiments

Embodiment 1

In this embodiment, an example of pasting a separated layer formed overa glass substrate by transfer on a plastic substrate is shown in FIGS.5A to 5J.

Here, a separation method using a metal film and a silicon oxide film isapplied.

First, an element is formed on a glass substrate (a first substrate300). In this embodiment, AN100 is used for the glass substrate. A metalfilm 301 a, which is a tungsten film (having a thickness ranging from 10nm to 200 nm, preferably, from 50 nm to 75 nm) here, is formed on theglass substrate by sputtering, and an oxide film 302, which is a siliconoxide film (having a thickness ranging from 150 nm to 200 nm) here, islaminated thereon without exposing to the air. The film thickness of theoxide film 32 shall preferably be twice or more than that of the metalfilm. Note that, while a lamination is formed, an amorphous oxide metalfilm (an oxide tungsten film) with a thickness ranging approximatelyfrom 2 nm to 5 nm is formed between the metal film 301 a and the siliconoxide film 302. In the occasion of a separation process thereafter,separation occurs in the oxide tungsten film, or at an interface betweenthe tungsten film and the oxide film, or an interface between the oxidetungsten film and a tungsten film.

In place of Tungsten (W), an element selected from a group consisting ofMolybdenum (Mo), WN, TiN, and TiW, or an alloy or a compound thereof maybe formed into a single layer or into a lamination thereof.

The tungsten film and the silicon oxide film are formed over an edgeportion and a side of the substrate in sputtering. It is preferable thatthe deposited tungsten film, the oxide tungsten film, and the siliconoxide film be removed selectively by O₂ ashing.

Next, a silicon oxynitride film as a base insulating film (with athickness of 100 nm) is formed by PCVD, and an amorphous silicon film(with a thickness of 54 nm) containing hydrogen is laminated thereonwithout exposing to the air. Note that, the silicon oxynitride film is ablocking layer which prevents impurities such as alkali metal fromdefusing out of a glass substrate.

A hydrogen concentration of the amorphous silicon film containinghydrogen was measured by FT-IR. As a result, Si—H was 1.06×10²²(atoms/cm³), Si—H₂ was 8.34×10¹⁹ (atoms/cm³), and the calculatedhydrogen concentration in the composition ratio was 21.5%. Further, thehydrogen concentration was similarly calculated under the changed filmdeposition conditions with PCVD; results of the obtained hydrogenconcentrations in the composition ratio were 16.4%, 17.1%, and 19.0%.

Thereafter, the amorphous silicon film is crystallized by using knowntechnique (solid-phase growth, laser crystallization, crystallizationusing catalyst metal, or the like), and an element using a TFT having apolysilicon film as an active layer is formed. In this embodiment, apolysilicon film is obtained by crystallization using a catalyst metal.A nickel acetate salt solution containing nickel of 10 ppm by weight iscoated by a spinner. Nickel elements can be applied on the entiresurface by sputtering instead of spin coating. Then, a heat treatment iscarried out to crystallize and form a semiconductor film having acrystal structure (here, a polysilicon layer). In this embodiment, asilicon film having a crystal structure is obtained by a heat treatmentfor crystallization (at 550° C. for 4 hours) after another heattreatment (at 550° C. for one hour).

The amorphous silicon film contains hydrogen. In the case of forming apolysilicon film by heating, a heat treatment at least at 410° C. isperformed thereby diffusing hydrogen as well as forming the polysiliconfilm. An amorphous oxide metal film is crystallized by a heat treatmentat least at 400° C. As a result, a metal oxide film 301 b having acrystal structure can be obtained. FIGS. 6A and 6B show across-sectional TEM picture. An oxide film having a crystallinestructure is formed accordingly and hydrogen is diffused by performing aheat treatment at least at 410° C. After the heat treatment at least at410° C. is finished, the separation in the oxide tungsten film, or at aninterface between the oxide tungsten film and the oxide silicon film, oran interface between the oxide tungsten film and the tungsten film canbe achieved with relatively little force (For example, human hands, windpressure of gas blown from a nozzle, or ultrasonic waves, or the like).Note that, when a heat treatment is performed at a temperature at whichan oxide metal film having a crystal structure can be obtained, athickness of the oxide metal film is thinned to some extent.

Various elements typified by a TFT (a thin film diode, a silicon-basedpin-junction photoelectric transducer, a silicon resistance element, asensor device (typically, a pressure-sensitive fingerprints sensor usingpolysilicon)) can be formed by using the obtained polysilicon film. Inaddition, the present invention can be applied to an element having aTFT that uses an amorphous silicon film as an active layer.

Next, after the oxide film on the surface of the silicon film having acrystal structure is removed by dilute hydrofluoric acid or the like,irradiation of laser light (XeCl: wavelength of 308 nm) for raising acrystallization rate and repairing defects remained in crystal grains isperformed in the atmosphere or in an oxygen atmosphere. Excimer laserlight with a wavelength of 400 nm or less, or second harmonic wave orthird harmonic wave of a YAG laser is used for the laser light. Here,pulsed laser light with a repetition frequency of approximately 10 to1000 Hz is used, the pulsed laser light is condensed to 100 to 500mJ/cm² by an optical system, and irradiation is performed with anoverlap ratio of 90 to 95%, whereby the silicon film surface may bescanned. Here, the irradiation of the laser light is performed in theatmosphere with a repetition frequency of 30 Hz and energy density of470 mJ/cm². Note that an oxide film is formed on the surface by thelaser light irradiation since the irradiation is conducted in theatmosphere or in an oxygen atmosphere. Though an example of using thepulsed laser is shown here, the continuous oscillation laser may also beused. When crystallization of an amorphous semiconductor film isconducted, it is preferable that the second harmonic through the fourthharmonic of basic waves is applied by using the solid state laser whichis capable of continuous oscillation in order to obtain a crystal inlarge grain size. Typically, it is preferable that the second harmonic(with a thickness of 532 nm) or the third harmonic (with a thickness of355 nm) of an Nd: YVO₄ laser (basic wave of 1064 nm) is applied.Specifically, laser light emitted from the continuous oscillation typeYVO₄ laser with 10 W output is converted into harmonics by using anon-linear optical elements. Also, a method of emitting harmonics byapplying crystal of YVO₄ and the non-linear optical elements into aresonator can be given. Then, more preferably, the laser beams areformed so as to have a rectangular shape or an elliptical shape by anoptical system, thereby irradiating a substance to be treated. At thistime, the energy density of approximately 0.01 to 100 MW/cm² (preferably0.1 to 10 MW/cm²) is required. The semiconductor film is moved atapproximately 10 to 2000 cm/s rate relatively corresponding to the laserbeams so as to irradiate the semiconductor film.

The oxide film formed by this laser light irradiation and an oxide filmformed by treating the surface with ozone water for 120 seconds togethermake a barrier layer that has a thickness of 1 to 5 nm in total. Thebarrier film is formed in order to remove nickel that is added forcrystallization from the film. Though the barrier layer is formed byusing ozone water here, another method such as ultraviolet irradiationperforming in an oxygen atmosphere or oxygen plasma treatment to oxidizethe surface of the semiconductor film having the crystal structure maybe used. In addition, as another method for forming the barrier layer,an oxide film having a thickness of about 1 nm to 10 nm may be depositedby plasma CVD, sputtering, evaporation, or the like. Further, beforeforming the barrier layer, the oxide film formed by laser lightirradiation may be removed.

On the barrier layer, an amorphous silicon film containing argonelements are formed to a thickness of 10 nm to 400 nm, in thisembodiment, 100 nm by sputtering to serve as a gettering site. In thisembodiment, an amorphous silicon film containing an argon element isformed under an atmosphere containing argon with using a silicon target.When plasma CVD is used for forming an amorphous silicon film containingargon element, it is formed under conditions where a flow ratio ofmonosilane to an argon is controlled to be 1/99; a pressure duringdeposition to be 6.665 Pa (0.05 Torr); a RF power density duringdeposition to be 0.087 W/cm²; a deposition temperature to be 350° C.

Thereafter, a furnace heated at 650° C. is used for a heat treatment for3 minutes for gettering to reduce the nickel concentration in thesemiconductor film having a crystal structure. A lamp annealingapparatus may be used instead of the furnace.

Subsequently, the amorphous silicon film containing the argon element,which is the gettering site, is selectively removed with the barrierlayer as an etching stopper, and then, the barrier layer is selectivelyremoved by dilute hydrofluoric acid. Note that there is a tendency thatnickel is likely to move to a region with a high oxygen concentration ingettering, and thus, it is desirable that the barrier layer comprised ofthe oxide film is removed after gettering.

Note that, in the case where crystallization is not performed using acatalytic element, the above described processes such as the formationof a barrier layer, the formation of a gettering site, a heat treatmentfor gettering, the removal of a gettering site, or the removal of abarrier layer are not necessary.

Then, after a thin oxide film is formed from ozone water on the surfaceof the obtained silicon film having a crystal structure (also referredto as polysilicon film), a mask made of resist is formed, and an etchingprocess is conducted thereto to obtain a desired shape, thereby formingthe island-like semiconductor layers separated from one another. Afterthe formation of the semiconductor layers, the mask made of resist isremoved.

Next, the oxide film is removed with the etchant containing hydrofluoricacid, and at the same time, the surface of the silicon film is washed.Thereafter, an insulating film containing silicon as its maincomponents, which serves as a gate insulating film, is formed. In thisembodiment, a silicon oxynitride film (composition ratio: Si=32%, 0=59%,N=7%, H=2%) is formed to have a thickness of 115 nm by PCVD.

Thereafter, gate electrodes are formed over a gate insulating film; theformation of a source region or a drain region attained by doping to theactive layer, the formation of an interlayer insulating film, theformation of a source electrode or a gate electrode, an activationtreatment, and/or the like is/are performed appropriately, and therebyfabricating a top gate TFT 303 which has a polysilicon film as an activelayer. Note that, FIGS. 5A to 5J shows a TFT for current control in thepixel region alone; however, a switching TFT or a driver circuit fordriving the pixel region are also formed on the same substrate.

Next, a film containing an organic compound (hereinafter, organiccompound layer) is interposed between a pair of electrodes (an anode anda cathode). Then, a first electrode for forming a light emitting devicethat can achieve fluorescence or phosphorescence by applying electricfield to the pair of electrodes is formed. Here, the first electrode 304that can serve as an anode or a cathode is formed of a large workfunction metal film (Cr, Pt, W, or the like), or a transparentconductive film (Indium tin oxide alloy (ITO), indium oxide zinc oxidealloy (In₂O₃—ZnO), zinc oxide (ZnO), or the like). An example of formingthe first electrode 304 for serving as an anode is described.

In case that the source electrode or the drain electrode of a TFT servesas a first electrode, or a first electrode in contact with the sourceregion or a drain region is formed separately, the TFT includes thefirst electrode.

A bank 305 a is formed on each end of the first electrode (anode) asencircling the periphery of the first electrode. To improve coverage,the upper edge portion or the bottom edge portion of the bank is formedto have a curved surface having curvature. For example, in the case thata positive type photosensitive acrylic is used as a material for thebank, it is preferable that only the upper edge portion of the bank isformed to have a curved surface having radius of curvature (from 0.2 to3 μm). Either a negative type that is an insoluble material in etchantaccording to light to which photosensitive material is exposed or apositive type that is dissoluble in etchant according to light can beused as the bank 305 a.

Further, in the case of laminating a plurality of organic resins, thereis a threat that a part of the plural organic resins is melted, or theplural organic resin is too adhesive, during application or baking.Therefore, in the case of using organic resin as a material for thebank, the bank 305 a is preferable to be covered by an inorganicinsulating film (a SiN_(x) film, a SiN_(x)O_(y) film, an AIN_(x) film,or an AIN_(x)O_(y) film) in order to make it easy to removewater-soluble resin after coating it over the whole surface in thefollowing process. The inorganic insulating film serves as a part of thebank 305 b (FIG. 5A).

Next, an adhesive that is soluble in water or alcohol is coated over thewhole surface and baked. The adhesive may be composed of, for example,epoxy series, acrylate series, silicon series, or the like. Here, a filmformed of water-soluble resin (TOAGOSEI Co., Ltd.: VL-WSHL10) 306 isspin-coated to have a thickness of 30 μm, and exposed for two minutes tobe partially cured, then, exposed its back to UV rays for 2.5 minutes,and then, exposed its surface for 10 minutes to be fully cured (FIG.5B). The water-soluble resin film serves as a leveling film, whichthereafter mates substrates together so a surface of the leveling filmand the substrate surface are placed in parallel. Unevenness mightgenerates resulting from an electrode or from a TFT when thewater-soluble resin film is not used, in pressure bonding.

The adhesion of the metal film 301 a and the metal oxide film 301 b, orthe adhesion of the metal oxide film 301 b and an oxide film 302 ispartly weakened for easy separation. The treatment for partly wakeningthe adhesion is carried out by applying laser light to the metal film301 b along the region that is to be separated, or damaging the insideor a part of the interface of the metal oxide film 301 b by applyingpressure locally from outside along to the region that is to beseparated. Specifically, a hard needle such as a diamond pen may beattached perpendicular to the region to be separated, and moved alongwith the periphery thereof by applying loading. Preferably, a scriberdevice can be used to move with applying loading on the region withpress force ranging from 0.1 to 2 mm. It is important to carry out someprocesses for easy separation, that is, prepare for the separationprocess. Such preparatory process for weakening selectively (partly) theadhesion will prevent poor separation and improve process yield.

Next, a second substrate 308 is pasted to a film 306 formed ofwater-soluble resin with a two-sided tape 307. Then, a third substrate310 is pasted to the first substrate 300 with a two-sided tape 309 (FIG.5C). The third substrate 310 prevents the first substrate 300 fromdamaging in the following separation process. For the second substrate308 and the third substrate 310, the substrate that has higher rigiditythan that of the first substrate 300, for example, a quartz substrate ora semiconductor substrate, is preferably to be used. Note that, anadhesive such as an adhesive which is separated by being exposed toultraviolet radiation may be used instead of a two-sided tape.

The first substrate 300 provided with the metal film 301 a is separatedfrom the region, which is partly weakened its adhesiveness by a physicalmeans. The first substrate 300 can be separated by comparatively smallforce (for example, man's hand, air pressure of gas sprayed from anozzle, ultrasonic waves, or the like). Thus, a layer to be separatedformed on the silicon oxide layer 302 can be separated from the firstelectrode 300. FIG. 5D shows a state after the separation process. Notethat, FIGS. 7A and 7B show a cross-sectional TEM picture of the firstsubstrate 300 which has undergone the separation. The TEM pictures inFIGS. 7A and 7B and FIGS. 6A and 6B show different parts and they do notcorrespond to each other. As shown in FIGS. 7A and 7B, the oxidetungsten film is partly thin and partly nonexistent. The tungsten oxidefilm partly remains in the separated layer; however, the tungsten filmis transparent, so that the film may not be necessarily removed. In thisembodiment, the film is removed.

By applying the separation method described above, a TFT having highelectric characteristics (typified by field effect mobility) can betransferred to a plastic substrate without change.

Next, a fourth substrate 312 is pasted to the oxide layer 302 (and theseparated layer) with an adhesive 311 (FIG. 5E). It is important thatthe adhesion of the fourth substrate 312 and the oxide layer 302 (andthe separated layer) is stronger than that of the second substrate 308and the separated layer by the two-sided tape 307.

A plastic substrate (ARTON made of norbornene resin with a polar group,manufactured by JSR) is used for the fourth substrate 312. The plasticsubstrate can be formed of at least one selected from the groupconsisting of: polyethylene terephthalate (PET), polyether sulfone(PES), polyethylene naphthalate (PEN), polycarbonate (PC), nylon,polyether ether ketone (PEEK), polysulfone (PSF), polyether imide (PEI),polyallylate (PAR), polybutylene terephthalate (PBT), and polyimide.

As the adhesive 311, various types of curing adhesive, for example, aphoto-curing adhesive such as a reaction-curing adhesive, a heat-curingadhesive, a UV-curing adhesive, or the like, or an anaerobic adhesive isutilized.

The second substrate 308 is separated from the two-sided tape 307 (FIG.5F).

Then, the two-sided tape 307 is removed (FIG. 5G).

And then, the water-soluble resin 306 is melted with water and removed(FIG. 5H). If residue of the water-soluble resin is left on the firstelectrode 304, it will cause the deterioration of the device.Consequently, it is preferable that the surface of the first electrode304 be rinsed or treated in O₂ plasma.

If it is necessary, the surface of the first electrode 304 is rubbed andwashed by using a porous sponge (typically, a sponge of PVA (polyvinylalcohol) or nylon) soaked in a surfactant (weak alkaline).

Immediately prior to forming a layer 313 containing an organic compound,the substrate is heated in a vacuum for removing absorbed moisture inthe whole substrate that is provided with a TFT and a bank. Moreover,the first electrode may be exposed to ultraviolet radiation immediatelyprior to forming the layer 313 containing the organic compound.

The layer 313 containing the organic compound is formed selectively overthe first electrode (anode) by vapor deposition using an evaporationmask or ink-jetting. As the layer 313 containing the organic compound, apolymer material, a low molecular material, an inorganic material, amixed layer formed of the above materials, a layer formed by dispersingabove materials, or a lamination layer formed by stacking appropriatecombination of the above materials can be used.

A second electrode (cathode) 314 is formed on the layer containing theorganic compound 303 (FIG. 5I). For forming the cathode 314, alamination layer of a thin film, which has a thickness of beingtransparent to light, formed of a small work function material (Al, Ag,Li, Ca, or alloy of these materials such as MgAg, MgIn, AlLi, CaF₂, orCaN) and a transparent conductive film is utilized. If necessary, aprotective layer is formed for covering the second electrode bysputtering or vapor deposition. The transparent protective laminationlayer may be formed of a silicon nitride film, silicon oxide film, asilicon nitride oxide film (SiNO film: a ratio of N to 0 composition isN>O)), or silicon oxynitride (SiON film: a ratio of N to 0 compositionis N<O), or a thin film containing carbon as its main component (forexample, DLC film, or CN film), formed by sputtering or CVD.

A sealing material (not shown) containing a spacer for maintaining a gapbetween a pair of substrates is applied to a fifth substrate 314 thatserves as a sealing member in a pattern of the first sealing materialshown in FIG. 1. The fifth substrate may be transparent to light in thisembodiment since an example of the light emitting element in which lightgenerated therein emit through the fifth substrate 314 is described.Here, the same plastic substrate (ARTON: JSR) as the fourth substrate isused to prevent a warp by conforming the thermal expansion coefficient.ARTON substrate is suitable for a fifth substrate since it is hardlybirefringent and has a low water absorption rate. When a plasticsubstrate is used, it is preferable that a pretreatment (ethanol wiping,UV radiation, O₂ plasma treatment or the like) for improving theadhesion between the plastic substrate and the first sealing materialbefore a pattern of the first sealing material is aligned.

Thereafter, a few drops of sealing material with a low viscosity areapplied to paste the sealing substrate and an active matrix substratewithout air bubbles mixed into using a pasting device shown in FIGS. 2Ato 2C or FIGS. 4A and 4B. The pasting device shown in FIGS. 2A to 2C andFIGS. 4A and 4B are of use particularly when a pair of plasticsubstrates is mated together. Moreover, applying a few drops of thesealing material with a low viscosity is also of use for pasting a pairof substrates together. With this pasting process, sealing is performedin a manner where a light emitting region provided on an active matrixsubstrate is surrounded by sealing patterns provided on a sealingsubstrate. Further, sealing is performed in a manner where a spacesurrounded by the sealing material is filled with an adhesive 315 formedfrom a transparent organic resin (FIG. 5J).

In the above step, a light emitting device provided with a TFT and alight emitting element can be manufactured with plastic substrates 312and 314 serving as holders. Since the holders are plastic substrates,the light emitting device can be thin, lightweight, and flexible. FIG. 8shows an active matrix light emitting device displaying images while itis folded with human fingers. The light emitting device shown in FIG. 8is manufactured according to this embodiment.

Here, an example of a light emitting device having a bottom emissionstructure is shown in FIGS. 9A and 9B.

Note that, FIG. 9A is a top view of the light emitting device and FIG.9B is a cross-sectional view of FIG. 9A taken along the line A—A′.Reference numeral 1201 indicated by the dotted line denotes a sourcesignal line driver circuit; 1202 denotes a pixel area; and 1203 denotesa gate signal line driver circuit. Further, reference numeral 1204 is aplastic substrate (ARTON); 1205 is a sealing material containing aspacer for maintaining a gap between a pair of substrates; and an insidearea surrounded by the sealing material 1205 is filled with a sealingmaterial 1207.

Note that, reference numeral 1208 denotes a wiring for transmittingsignals inputted to the source signal line driver circuit 1201 and thegate signal line driver circuit 1203, and the wiring receives videosignals and clock signals form an FPC (flexible printed circuit) 1209serving as an external input port.

Next, a cross-sectional structure will be explained with reference toFIG. 9B. A driver circuit and a pixel area are formed over a substrate1210 having transparency with an adhesive 1240 therebetween, but thesource signal line driver circuit 1201 as the driver circuit and thepixel area 1202 are shown in FIG. 9B. The source signal line drivercircuit 1201 is formed of a CMOS circuit that is a combination of ann-channel TFT 1223 and a p-channel TFT 1224.

The pixel area 1202 is formed from a plurality of pixels each of whichincludes a switching TFT 1211, a current controlling TFT 1212, and afirst electrode (anode) 1213 formed of a transparent conductive filmthat is electrically connected to a drain of the current controlling TFT1212.

In this embodiment, the first electrode 1213 is formed so that a part ofwhich is to be overlapped with a connecting electrode so as to beelectrically connected to a drain region of the TFT via the connectingelectrode. It is preferable that the first electrode 1213 be formed of aconductive film that has transparency and a large work function (forexample, an indium tin oxide alloy (ITO), an indium oxide-zinc oxidealloy (In₂O₃—ZnO), zinc oxide (ZnO), or the like).

An insulator 1214 (referred to as a bank, or the like) is formed tocover the edge portion of the first electrode (anode) 1213. To improvecoverage, the upper edge portion or the lower edge portion of theinsulating substance 1214 b is formed to have a curved surface having acurvature. In addition, the insulator 1214 may be covered with aprotective film formed of an aluminum nitride film, an aluminum nitrideoxide film, a thin film containing carbon as its main components, or asilicon nitride film.

An organic compound layer 1215 is selectively formed over the firstelectrode (anode) 1213 by vapor deposition using an evaporation mask orink-jetting. Further, a second electrode (cathode) 1216 is formed overthe organic compound layer 1215. As a material for forming the cathode,a small work function material (for example Al, Ag, Li, Ca, alloysthereof, that is, MgAg, MgIn, AlLi, CaF₂, or CaN) may be used. Thus, alight emitting device 1218 comprising the first electrode (anode) 1213,the organic compound layer 1215, and the second electrode (cathode)1216, is fabricated. The light emitting device 1218 emits light in thedirection indicated by an arrow in FIG. 9B. The light emitting device1218 in this embodiment is a type of the one which can achievemonochrome emission of R, G, or B. Full color emission can be achievedby the light emitting device in which each organic compound layer thatcan achieve R, G, and B emission is formed selectively.

Further, a protective layer 1217 is formed in order to seal the lightemitting element 1218. The transparent protective layer 1217 may bepreferably formed of an insulating film containing silicon nitride orsilicon nitride oxide as it main components, which is formed bysputtering (DC type of RF type) or PCVD, a thin film containing carbonas its main component (for example, DLC film, or CN film), or alamination layer comprising the above. A silicon nitride film havinghigh blocking effects against impurities such as moisture, alkalimetals, or the like can be obtained by using a silicon target under anatmosphere comprising nitrogen and argon. A silicon nitride target maybe utilized instead of using a silicon target. In addition, thetransparent protective film can be formed by a film formation systemthat uses remote plasma.

Further, in order to seal the light emitting element 1218, the plasticsubstrate 1204 is pasted to the substrate by the first sealing material1205 and the second sealing material 1207 under an inert gas atmosphere.It, is preferable to use an epoxy resin with high viscosity comprisingfiller as a material for the first sealing material 1205. The secondsealing material is preferably formed from an epoxy resin having a lowviscosity as well as high transparency. It is also preferable that thesealing material 1025 and 1207 inhibit transmission of moisture oroxygen as possible.

Further that, a substrate 1210 is a plastic substrate (ARTON) pastedafter the formation of a TFT. Note that, a substrate to which thesubstrate 1210 is to be pasted is separated according to the aboveseparation method.

Here, the separation is carried out in the vicinity of an interface ofthe oxide tungsten film; however, it is not limited to such a method.For example, the separation may be achieved by laser irradiation afteran amorphous silicon film containing hydrogen is formed over a firstsubstrate, or a first substrate may be removed by etching or by machine.

Further, this embodiment can freely be combined with Embodiment Mode 1or Embodiment Mode 2

Embodiment 2

In Embodiment 1, an example of pasting a plastic substrate is shown;however, the present invention can be applied to other types ofsubstrate pasting. In this embodiment, an example of manufacturing alight emitting device (top emission structure) provided with a lightemitting element having an organic compound layer as a light emittinglayer is shown in FIGS. 10A and 10B.

The conventional light emitting device has a structure that has a lightemitting element in which an electrode on a substrate is formed as ananode, an organic compound layer is formed on the anode, and a cathodeis formed on the organic compound layer, and light generated in theorganic compound layer is emitted through the anode formed as atransparent electrode to a TFT (hereafter, the structure is referred toas a bottom emission).

Although an encapsulating can is possible to cover a light emittingelement in the above bottom emission structure, the structure in whichan electrode on a substrate is formed as an anode, an organic compoundlayer is formed on the anode, and a cathode as a transparent electrodeis formed over an organic compound layer (hereinafter, the structure isreferred to as a top emission structure) cannot use the encapsulatingcan that is made from a light shielding material. A desiccant on thepixel area disturbs the display in the top emission structure. Further,in order not to absorb moisture, the desiccant requires careful handlingand quick enclosing.

Compared to a bottom emission structure, a top emission structurerequires few material layers through which light generated in an organiccompound layer is transmitted, and thereby suppresses stray lightbetween material layers having different reflective index.

In this embodiment, the glass substrate 1104 and the glass substrate1110 are pasted together by the pasting method and pasting deviceaccording to Embodiment Mode 1 or Embodiment Mode 2.

FIG. 10A is a top view of a light emitting device. FIG. 10B is across-sectional view of FIG. 10A taken along the line of A—A′. Referencenumeral 1101 denoted by a dotted line denotes a source signal linedriver circuit; 1102 denotes a pixel area; 1103, a gate signal linedriver circuit; 1104, a transparent sealing substrate; and 1105, a firstsealing material. Space encircled by the first sealing material 1105 isfilled with a transparent second sealing material 1107. In addition, thefirst sealing material 1105 contains a spacer for maintaining a gapbetween substrates.

Further, reference numeral 1108 denotes a wiring for transmittingsignals inputted to the source signal line driver circuit 1101 and thegate signal line driver circuit 1103. The wiring 1108 receives a videosignal or clock signal from a FPC (flexible printed circuit) 1109 thatserves as an external input terminal. Although only FPC is illustrated,a printed wiring board (PWB) may be attached to the FPC.

The cross-sectional structure will be described with reference to FIG.10B. A driver circuit and a pixel region are formed over a glasssubstrate 1110 with a laminated film 1150 and an adhesive 1140therebetween. A source signal driver circuit 1101 as a driver circuitand a pixel region 1102 are shown here.

In the source signal line driver circuit 1101 is formed from a CMOScircuit in which an n-channel TFT 1123 and a p-channel TFT 1124 arecombined. Note that, such TFTs can also be obtained according toEmbodiment 1. The TFTs which form the driver circuit may be formed by atleast one circuit selected from the group consisting of: a CMOS circuit,a PMOS circuit and an NMOS circuit which are known in the art. In thepresent embodiment, a driver-integrated type in which the driver circuitis formed over the substrate is shown, but the driver-integrated typemay not necessarily be adopted. The driver circuit can also be formedoutside instead of being formed over the substrate. A constitution ofthe TFT using a polysilicon film as an active layer is not particularlylimited thereto, either a top gate type TFT or a bottom gate type TFT ispermissible.

The pixel area 1102 is formed by a plurality of pixels each of whichcomprises a switching TFT 1111, a current-controlling TFT 1112 and afirst electrode (anode) 1113 which is electrically connected to thedrain of the current-controlling TFT 1112. The current-controlling TFT1112 may either be an n-channel type TFT or a p-channel type TFT, butwhen it is to be connected to the anode, it is preferably be a p-channeltype TFT. It is also preferable that a storage capacitor (not shown) isappropriately provided. An example in which only a cross-sectionalconstitution of one pixel is shown where two TFTs are used in the pixelis illustrated, but three or more TFTs may appropriately be used perpixel.

Since it is constituted such that the first electrode 1113 is directlyconnected to the drain of the TFT 1112, it is preferable that a lowerlayer of the first electrode 1113 be a material layer which can have anohmic contact with the drain comprising silicon, while an uppermostlayer thereof which contacts a layer containing an organic compound isallowed to be a material layer which has a large work function. Forexample, a three-layer constitution which includes a titanium nitridefilm, a film containing aluminum as a main component, and a titaniumnitride film, can have a low resistance of wiring, a favorable ohmiccontact, and also, can function as an anode. Further, as the firstelectrode 1113, a single layer of at least one film selected from thegroup consisting of: a titanium nitride film, a chromium film, atungsten film, a zinc film, a platinum film and the like, or a laminateof three layers or more may be used.

An insulating substance 1114 (referred to as a bank, a partition, abarrier, a mound or the like) is formed over each end of the firstelectrode (anode) 1113. The insulating substance 1114 may be formed byeither an organic resin film or an insulating film comprising silicon.In the present embodiment, as for the insulating substance 1114, aninsulating substance is formed in a shape as shown in FIGS. 10A and 10Bby using a positive type photosensitive acrylic resin film.

For the purpose of enhancing a coverage effect, a curved surface havinga curvature is to be formed in an upper end portion or a lower endportion of the insulating substance 1114. For example, when the positivetype photosensitive acrylic resin is used as a material for theinsulating substance 1114, it is preferable that a curved face having acurvature radius (0.2 μm to 3 μm) is provided only to the upper endportion of the insulating substance 1114. As for the insulatingsubstance 1114, either one of a negative type which becomes insoluble toan etchant by photosensitive light, and a positive type which becomessoluble to the etchant by the light can be used.

Further, the insulating substance 1114 may be covered by a protectivefilm comprising at least one film selected from the group consisting of:an aluminum nitride film, an aluminum oxynitride film, a thin filmcontaining carbon as a main component, and a silicon nitride film.

A layer 1115 containing an organic compound is selectively formed overthe first electrode (anode) 1113 by vapor deposition using vapor mask orink-jetting. Further, a second electrode (cathode) 1116 is formed overthe layer 1115 containing the organic compound. As for the cathode, amaterial having a small work function (for example Al, Ag, Li, Ca,alloys of thereof, that is, MgAg, MgIn, AlLi, CaF₂, or CaN) may be used.In the present embodiment, in order to allow luminescence to passthrough, as for the second electrode (cathode) 1116, a thin metal filmwhich is thin in thickness is formed, and a transparent conductive film(for example, an indium oxide-tin oxide alloy (ITO), an indiumoxide-zinc oxide alloy (In₂O₃—ZnO), zinc oxide (ZnO)), or the likeis/are laminated thereover. Note that the transparent conductive film isformed in order to reduce the electric resistance. Then, a lightemitting element 1118 comprising the first electrode (anode) 1113, thelayer 1115 containing the organic compound, and the second electrode(cathode) 1116 is fabricated. In the present embodiment, the lightemitting element 1118 shall be an example of emitting white light; andtherein, a color filter (for the purpose of simplicity, an overcoatlayer is not shown) comprising a colored layer 1131 and a light blockinglayer (BM) is provided.

Further, when layers each containing an organic compound which canobtain R, G, and B luminescence respectively, are selectively formed, afull-color display can be obtained without using a color filter.

A transparent protective layer 1117 is formed in order to seal the lightemitting element 1118. The transparent protective layer 1117 may bepreferably formed of an insulating film containing silicon nitride orsilicon nitride oxide as its main components, which is formed bysputtering (DC type of RF type) or PCVD, a thin film containing carbonas its main component (for example, DLC film, or CN film), or alamination layer comprising the above. A silicon nitride film havinghigh blocking effects against impurity elements such as moisture, alkalimetals, or the like can be formed by using a silicon target under anatmosphere comprising nitrogen and argon. A silicon nitride target maybe used alternatively. In addition, the transparent protective layer canbe formed by a film formation system that uses remote plasma. It ispreferable that the total thickness of the transparent protective layerbe formed to be thin as far as possible in order that light may passthrough the transparent protective layer.

Further, in order to seal the light emitting element 1118, the sealingsubstrate 1104 is pasted to the substrate by the first sealing material1105 and the second sealing material 1107 under an inert gas atmosphere.It is preferable to use such as an epoxy resin as a material for thefirst sealing material 1105 and the second sealing material 1107. It isalso preferable that the first sealing material 1105 and the secondsealing material 1107 inhibit transmission of moisture or oxygen aspossible.

By sealing the light emitting element with the first sealing material1105 and the second sealing material 1107 as described above, it becomespossible that the light emitting device can be completely encapsulatedand penetration of moisture or oxygen from outside that causesdeterioration of the light emitting element can be prevented.

This embodiment can be freely combined with any one of Embodiment Mode1, Embodiment Mode 2, and Embodiment 1.

Embodiment 3

In this embodiment, an example of a sealing pattern different from theone in Embodiment Mode 1 is shown in FIG. 11.

An example of a top view of a sealing substrate (a second substrate 72)before pasting is shown in FIG. 11A. An example of forming a lightemitting device having one pixel area from one substrates is shown inFIG. 11A.

Six bars of a first sealing material 76 are formed first on the secondsubstrate 72 which is plastic by using a dispenser; thereafter, a fewdrops of a second sealing material having a lower viscosity than that ofthe first sealing material is applied thereon. The first sealingmaterial 76 is arranged so as not to reach to terminal areas. FIG. 11Ashows a top view of the state where the sealing material is applied tothe substrate. Note that, the second substrate 72 which is plastic isshaped into a desired size beforehand.

The second substrate is then pasted a first substrate 71 provided with apixel area 73 having light emitting elements, or a driver circuitportion 74 and a terminal area 75. The first substrate 71 may be a glasssubstrate or a plastic substrate. Note that, since a warp might begenerated when the thermal expansion coefficients of the two substratesare different, the first substrate 71 may be formed from a materialhaving the same coefficient of thermal expansion as the secondsubstrate. A top view of the state immediately after pasting the pair ofsubstrates is shown in FIG. 11B. The viscosity of the first sealingmaterial is high, and therefore it spreads out very little upon pasting.The viscosity of the second sealing material is low; accordingly, thesecond sealing material spreads out planarly upon pasting. The secondsealing material is squeezed out between the bars of the first sealingmaterial 76, that is, in the direction of an arrow in FIG. 11B, towardopening portions. Air bubbles can thus be kept from existing in a regionbetween the bars of the first sealing material 76, which is filled withthe second sealing material. The first sealing material 76 does not mixwith a second sealing material 77 b, even if there is contact, and thefirst sealing material 76 has a viscosity such that the position atwhich it is formed is not changed by the second sealing material 77 b.Note that, the first sealing material 76 includes a spacer (filler,minute particles and/or the like) which maintains a gap between the twosubstrate.

This embodiment can be freely combined with any one of Embodiment Mode1, Embodiment Mode 2, Embodiment 1, or Embodiment 2.

Embodiment 4

Electronic devices can be produced by employing a light emitting deviceobtained by implementing the present invention to a display portiontherein. Examples of the electronic devices can be given as a videocamera, a digital camera, a goggle type display (head mounted display),a navigation system, an audio reproducing apparatus (car audio, an audiocomponent, and the like), a laptop computer, a game machine, a portableinformation terminal (a mobile computer, a cellular phone, a portablegame machine, an electronic book, etc.), and an image reproducingapparatus including a recording medium (specifically, an apparatuscapable of processing data in a recording medium such as a DigitalVersatile Disk (DVD) and having a display that can display the image ofthe data). Practical examples thereof are shown in FIGS. 12A to 12H.

FIG. 12A shows a television, which comprises a casing 2001, a supportingbase 2002, a display portion 2003, speaker units 2004, a video inputterminal 2005, etc. The present invention is applied to the displayportion 2003. The term television includes every television fordisplaying information such as one for a personal computer, one forreceiving TV broadcasting, and one for advertisement.

FIG. 12B shows a digital camera, which comprises a main body 2101, adisplay portion 2102, an image receiving unit 2103, operation keys 2104,an external connection port 2105, a shutter 2106, etc. The presentinvention is applied to the display portion 2102.

FIG. 12C shows a laptop computer, which comprises a main body 2201, acasing 2202, a display portion 2203, a keyboard 2204, an externalconnection port 2205, a pointing mouse 2206, etc. The present inventionis applied to the display portion 2203.

FIG. 12D shows a mobile computer, which comprises a main body 2301, adisplay portion 2302, a switch 2303, operation keys 2304, an infraredray port 2305, etc. The present invention is applied to the displayportion 2302.

FIG. 12E shows a portable image reproducing apparatus equipped with arecording medium (a DVD player, to be specific). The apparatus comprisesa main body 2401, a casing 2402, a display portion A 2403, a displayportion B 2404, a recording medium (such as DVD) reading unit 2405,operation keys 2406, speaker units 2407, etc. The display portion A 2403mainly displays image information whereas the display portion B 2404mainly displays text information. The present invention is applied tothe display portions A 2403 and B 2404. The term image reproducingapparatus equipped with a recording medium includes domestic gamemachines.

FIG. 12F shows a game machine, which comprises a main body 2501, displayportions 2505, and an operation switch 2504. The present invention isapplied to the display portion 2505.

FIG. 12G shows a video camera, which comprises a main body 2601, adisplay portion 2602, a casing 2603, an external connection port 2604, aremote control receiving unit 2605, an image receiving unit 2606, abattery 2607, an audio input unit 2608, operation keys 2609 etc. Thepresent invention is applied to the display portion 2602.

FIG. 12H shows a cellular phone, which comprises a main body 2701, acasing 2702, a display portion 2703, an audio input unit 2704, an audiooutput unit 2705, operation keys 2706, an external connection port 2707,an antenna 2708, etc. The present invention is applied to the displayportion 2703. Power consumption of the cellular phone can be reduced bydisplaying white characters on a black background in the display portion2703.

As described above, the light emitting device obtained by implementingthe present invention may be used as display portions of any electronicdevice. The electronic devices described in this embodiment may use anystructure of a light emitting device shown in Embodiment Modes 1,Embodiment Mode 2, or Embodiments 1 through 3.

According to the present invention, when a pair of substrates(particularly, flexible plastic substrates) is pasted together, a spacebetween two substrates can be filled with a transparent sealing materialwithout air bubbles mixing in. Thus, a light emitting device with highreliability can be obtained.

1. A manufacturing method of a light emitting device including a pixelportion provided with a plurality of light emitting elements having afirst electrode, an organic compound layer in contact with a top portionof the first electrode, and a second electrode in contact with a topportion of the organic compound layer, between a pair of substrates, atleast one of which is transparent, the manufacturing method of a lightemitting device comprising the steps of: forming a pixel portion overone of the substrates; figuring a first sealing material having a barshape on the other substrate; applying a plurality of drops of a secondsealing material having lower viscosity than the first sealing materialto a region surrounded by the first sealing material so that an amountof drops differs depending on a region to be applied to; and pasting thepair of substrates so that the first sealing material is arranged tosurround the pixel region, and a space between at least a pair of thefirst sealing materials is filled with the second sealing material,wherein the second sealing material is applied at least to a centralpart of the pixel portion and to a position surrounding the centralpart.
 2. A manufacturing method of a light emitting device according toclaim 1, wherein an amount of the second sealing material applied to thecentral part is larger than an amount applied to the positionsurrounding the central part.
 3. A manufacturing method of a lightemitting device according to claim 1, wherein the first sealing materialhas opening portions at least at four corners.
 4. A manufacturing methodof a light emitting device according to claim 1, wherein the firstsealing material includes a spacer for maintaining a gap between a pairof substrates.
 5. A manufacturing method of a light emitting deviceaccording to claim 1, wherein the second sealing material is exposed atthe opening portion, and a peripheral border of the exposed secondsealing material is curved.
 6. A manufacturing method of a lightemitting device according to claim 1, wherein the second sealingmaterial is exposed at the opening portion, and peripheral border of theexposed second sealing material protrudes from the opening portion.
 7. Amanufacturing method of a light emitting device including a pixelportion provided with a plurality of light emitting elements having afirst electrode, an organic compound layer in contact with a top portionof the first electrode, and a second electrode in contact with a topportion of the organic compound layer, between a pair of substrates, oneof which is transparent, the manufacturing method of a light emittingdevice comprising the steps of: forming a pixel portion on one of thesubstrates; figuring a first sealing material having a bar shape on theother substrate; applying a plurality of drops of a second sealingmaterial having lower viscosity than the first sealing material to aregion surrounded by the first sealing material so that an amount ofdrops differs depending on a region to be applied to; filling a spacebetween the first sealing materials facing one another, by spreading thesecond sealing material under pressure in the case where a pair of thesubstrates is pasted together so that the pixel region is surrounded bythe first sealing material; and curing the first sealing material andthe second sealing material, wherein the second sealing material isapplied at least to a central part of the pixel portion and to aposition surrounding the central part.
 8. A manufacturing method of alight emitting device according to claim 7, wherein the curing of thefirst sealing material and the second sealing material is performed byexposure to ultraviolet radiation or by heat.
 9. A manufacturing methodof a light emitting device according to claim 7, wherein a pair of thesubstrates is divided vertically to the first sealing material aftercuring the first sealing material and the second sealing material.
 10. Amanufacturing method of a light emitting device comprising the steps of:forming a pixel portion over a first substrate; forming a first sealingmaterial having a bar shape on a second substrate; applying a pluralityof drops of a second sealing material having lower viscosity than thefirst sealing material to a region surrounded by the first sealingmaterial so that an amount of drops differs depending on a region to beapplied to; and pasting the pair of substrates so that the first sealingmaterial is arranged to surround the pixel region, and a space betweenat least a pair of the first sealing materials is filled with the secondsealing material, wherein the second sealing material is applied atleast to a central part of the pixel portion and to a positionsurrounding the central part.
 11. A manufacturing method of a lightemitting device comprising the steps of: forming a pixel portion over afirst substrate; forming a first sealing material having a bar shape ona second substrate; applying a second sealing material having lowerviscosity than the first sealing material to a first region and a secondregion which are surrounded by the first sealing material so that anamount of drops to the first region is larger than that to the secondregion; and pasting the pair of substrates so that the first sealingmaterial is arranged to surround the pixel region, and a space betweenat least a pair of the first sealing materials is filled with the secondsealing material, wherein the second sealing material is applied atleast to a central part of the pixel portion and to a positionsurrounding the central part.
 12. A manufacturing method of a lightemitting device according to claim 7, wherein an amount of the secondsealing material applied to the central part is larger than an amountapplied to the position surrounding the central part.
 13. Amanufacturing method of a light emitting device according to claim 10,wherein an amount of the second sealing material applied to the centralpart is larger than an amount applied to the position surrounding thecentral part.
 14. A manufacturing method of a light emitting deviceaccording to claim 11, wherein an amount of the second sealing materialapplied to the central part is larger than an amount applied to theposition surrounding the central part.